The invention relates to heaters for engines, and more particularly, preheaters for watercooled diesel engines. The invention also relates to multi-stage heat exchangers and fuel burners.
It is well known that engines, particularly diesel automobile and truck engines, and off highway equipment, are difficult to start in cold weather. Cold weather adversely affects fuel ignition, increases the viscosity of engine lubricants making it more difficult to crank the engine, and reduces the electrical power outputs of storage batteries for cranking the engine. Many attempts have been made to solve these problems. For example, the following U.S. Patents disclose various devices for heating engines:
______________________________________ U.S. Pat. No. Date Inventor ______________________________________ 3,796,207 03-12-74 Olson 3,758,031 09-11-73 Moran 2,737,169 03-06-56 Kimberlin 2,695,603 11-30-54 Williams 2,681,052 06-15-54 Kazial 2,627,258 02-03-53 Mariska ______________________________________
The devices disclosed by the above listed patents and other prior engine heaters are generally adapted for heating truck engines overnight. But, such devices are generally not suitable for rapidly preheating engines.
There are several primary drawbacks in the prior art. First, the prior art teaches low efficiency single stage heat exchangers, i.e., the surface area of the heat exchanger is relatively low as compared to the volume of coolant to be heated. This is due to the tendency of soot to build up on the relatively cool heat exchanger walls, necessitating large unobstructed passages through the heat exchanger. Because of their low efficiency, these heaters are suitable for overnight heating, but not for rapid preheating.
A second drawback is the size of the heaters. Because of their low efficiency, relatively large heaters are required. This is a problem for automobile applications where there is limited space available under the hood.
Another drawback is that the prior art devices heat the engine block, but not the engine battery compartment. It would be desirable to also heat the battery to increase the power available for cold cranking.
The burners employed in the prior art heaters are of several types, each with attendant disadvantages. One variety of burner is a gaseous fuel burner. The disadvantage here is that an additional fuel tank is required, apart from the vehicle fuel tank, for the gaseous fuel. A second variety of burner is a wick type liquid fuel burner. This is preferable to gaseous fuel burners because an additional fuel tank is not required. However, these burners are typically gravity fed, which means that they must be positioned below the fuel tank; they tend to leak fuel; and their combustion efficiency cannot be controlled. The third variety of burner is a fuel spray nozzle with high voltage spark ignition. The attendant disadvantage of these burners is that the spray nozzles occasionally clog, require high fuel delivery pressures, and high voltage ignition is a drain on the power supply.
It would be desirable to have an efficient engine preheater, that will rapidly warm the engine and also warm the vehicle battery compartment, that is sufficiently small in size for use in automobiles, and that employs a controllable liquid fuel burner that does not require high voltage ignition.